How can I render in blender via GPU on my 64 bit PC that has Intel HD graphics 620 as well as radeon 27 m445 display adapters?
First, the radeon is an AMD graphics card, not an NVidia, so you won't find drivers for it on NVidia's site.

Second, while blender can use openCL, it demands a reasonably modern GPU. Yours seems to be a bit older, so not sure blender will be able to use it, even with the proper drivers. (see the blender documentation for more details)